Neuro Imaging Project on Rett Syndrome This project consists of three major components and goals. They are: Firstly, to determine if the level of dopamine transporters is abnormal in Rett Syndrome (RS) as compared to age and sex-matched controls. Secondly, to determine if endogenous dopamine response to dextromethorphan is abnormal in RS as compared to the response in control subjects using 11/C-Raclopride. Thirdly, to determine the structural and volumetric brain changes as a function of age in RS. Supportive areas of methodological validation will be carried out prior and simultaneous to these studies. For the PET these include continued study of the effect of various anesthetics on the dopamine transporter and endogenous dopamine measurements. Also needed is correction for the reduction in volume seen in the basal ganglia in RS patients as a function of time in order to provide valid comparisons of PET measurements between RS and controls. Furthermore, a brain map, a new application to MRI, will be applied prior to the partial volume corrections for the PET and the volumetric studies with MRI to indicate specific areas where additional effort can be made. All of these imaging efforts will be coordinated and integrated. They should provide important new information concerning the neurophysiological abnormalities in RS and the areas of structural change from which additional neurochemical and neuropharmacological correlates can be made.